Among fuel cells for generating electric power utilizing an electrochemical reaction between hydrogen and oxygen, polymer electrolyte fuel cells are commonly known. The polymer electrolyte fuel cell includes a stack which is constituted from a plurality of stacked cells. The cells constituting the stack each include an anode (fuel electrode) and a cathode (air electrode), and a solid polymer electrolyte membrane having a sulfonic acid group as an ion exchange group is interposed between each anode and cathode.
A fuel gas containing a fuel gas (hydrogen-enriched reformed hydrogen obtained by reforming hydrogen gas or hydrocarbon) is supplied to the anode, while a gas containing oxygen as an oxidant (oxidant gas), e.g., air, is supplied to the cathode. Upon the supply of the fuel gas to the anode, hydrogen contained in the fuel gas reacts with a catalyst in a catalyst layer which constitutes the anode, thereby generating hydrogen ions. The generated hydrogen ions pass through the solid polymer electrolyte membrane and electrically react with oxygen in the cathode. Electric power is thus generated through the electrochemical reaction.
Here, Patent Document 1 below discloses a technique in which a fuel cell is started with a short supply of at least one of a fuel gas supplied to an anode and an oxidant gas supplied to a cathode, so that overvoltage in a part of the electrodes will increase and more heat will be generated, thereby increasing the temperature of the fuel cell.
Patent Document 1: JP2003-504807 T